In general, an electronic circuit board case configured to accommodate an electronic circuit board is required to have a waterproof property to restrict permeation of water, in consideration of exposure to dew condensation and spray of water. It is conceivable to provide a sealing member in a joined portion of an electronic circuit board case to enhance waterproof property. However, provision of a sealing member requires additional sealing member and additional manufacturing process for equipping the sealing member to the electronic circuit board case. In consideration of this, for example, JP-A-H10-135649 discloses an electronic circuit board case having waterproof property without using a sealing member. However, the configuration of JP-A-H10-135649 may not have a sufficient waterproof property.